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11-06-2018, 06:50 AM
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Join Date: Dec 2012
Location: Greenback, TN
Posts: 534
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RV14 CHT and Oil temperatures
For the purposes of this thread I elected to post only ROP (Rich of Peak) data at or above 70% power (worst case). As you can see the RV-14 cooling system leaves significant margin for CHT cooling. Oil temperature is what I find more limiting, but still quite acceptable. I have eventual plans for a cowl flap and this data shows careful placement of the oil cooler exit in an area of low pressure will be necessary.
This data was collected over 16 months and 230 hours of flight time. THE AREAS CIRCLED IN YELLOW ARE DURING ENGINE BREAK IN.
CONDITIONS:
Percent Power between 70 and 75%
Stabilized in cruise flight at 100ROP for 2 to 7 minutes.
Altitude various but always high enough to be WOT.
NOTE: Timing in this data varies from 20 to 24 BTDC accounting for some temperature variations. 23BTDC was the best condition for speed; however, it did increase the temperatures. The breakin temperatures in the yellow circles are all at 20BTDC.

__________________
Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 500+
2020 Dues Paid
The Dues Paid note is a reminder for me
Last edited by M McGraw : 11-24-2019 at 07:27 PM.
Reason: Updated picture link
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11-06-2018, 08:22 AM
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Join Date: Feb 2005
Location: Wisconsin
Posts: 612
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I don't think you have anything to worry about, Chris. My RV14 CHTs are significantly better than my IO-540 in the RV-10. They're lower than expected. The engine gets very good cooling. I just added an oil cooler throttle valve too, because my oil temps get too low in the cold weather.
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11-06-2018, 08:43 PM
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Join Date: Feb 2014
Location: berrien center, mi
Posts: 16
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Hi Jesse. Actually the temps rarely get over 320 during climb at 100 knots on a hot day with 300 in cruise with oil temps around 200. Autumn temps now are running about 270 in cruise and oil temps are 190. That's a OAT of 33 F.
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11-06-2018, 09:42 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Marvin was the only respondent to note ignition timing, a very significant CHT factor.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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11-07-2018, 06:33 AM
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Join Date: Mar 2014
Location: Granbury, TX
Posts: 268
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Ignition timing is, of course, important. However, for the 390 (in my case XP-400) it seems that CHT is less of an indicator. I have dual PMags and I have run my engine timed 20? BTDC., 25? BTDC, jumper in and jumper out (even more advanced) with very little change in observed CHTs. In discussions with Superior, I believe the extended stroke of this engine opens the sweet spot and makes it less sensitive to timing changes.
__________________
Keith Brown
RV-14A Builder - kit #136
N314KC - First flight Mar 8, 2017, 24th in the air, >600 hrs
XP-400 Aero Sport Power, replaced with Lyc Thunderbolt 390
RV-6A sold
Sport Pilot (weight-shift control) - Airborne XT912
Dues paid 9/2020
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11-07-2018, 07:57 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by KeithB
Ignition timing is, of course, important. However, for the 390 (in my case XP-400) it seems that CHT is less of an indicator. I have dual PMags and I have run my engine timed 20? BTDC., 25? BTDC, jumper in and jumper out (even more advanced) with very little change in observed CHTs. In discussions with Superior, I believe the extended stroke of this engine opens the sweet spot and makes it less sensitive to timing changes.
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Don't know about a sweet spot, but FWIW, the 390 has the same stroke as the 360.
Care to quantify "very little change"? Last check I made said running 20~30 LOP results in approximately 1.6 degrees F per degree of advance, which matches Nigel's data for his parallel valve. I would expect 2.5 degrees per degree running ROP.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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11-07-2018, 08:39 AM
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Join Date: Dec 2012
Location: Greenback, TN
Posts: 534
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CHT as a function of ignition advance
This is for 75% power at 100ROP and constant OAT. I stopped testing at 25BTDC because temperature continued to increase and speed decreased indicating I had exceeded a useful advance. Speed peaked at 23BTDC.

__________________
Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 500+
2020 Dues Paid
The Dues Paid note is a reminder for me
Last edited by M McGraw : 11-07-2018 at 08:47 AM.
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11-07-2018, 09:02 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
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Quote:
Originally Posted by M McGraw
This is for 75% power at 100ROP and constant OAT. I stopped testing at 25BTDC because temperature continued to increase and speed decreased indicating I had exceeded a useful advance. Speed peaked at 23BTDC.

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A similar data display at 20 degrees or so LOP would be appreciated.
Carl
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11-07-2018, 10:07 AM
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Join Date: Dec 2012
Location: Greenback, TN
Posts: 534
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CHT LOP data
Hello Carl,
I do have LOP data. In fact, I have too much. This is my first engine which could run LOP so I tested way too many variables to understand the effects. I only post data that has been repeated at least three times. That was easy for ROP because I did everything at +100. For LOP I tested -25, -50, -75, -100, etc... I focused more on speed and fuel flow since CHT was always lower than the ROP number and my goal is to create a cowl flap; that exit dimension is controlled by the ROP temps.
A summary would be that 25LOP CHTs increase by less than 2 degrees per degree of ignition advance.
__________________
Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 500+
2020 Dues Paid
The Dues Paid note is a reminder for me
Last edited by M McGraw : 11-07-2018 at 10:10 AM.
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11-07-2018, 11:40 AM
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Join Date: Mar 2014
Location: Granbury, TX
Posts: 268
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It looks like there are differences between the original (Lycoming) and the clone (Superior). The XP400 is stroked an additional 0.25?. Whether or not that is material is beyond my pay grade.
__________________
Keith Brown
RV-14A Builder - kit #136
N314KC - First flight Mar 8, 2017, 24th in the air, >600 hrs
XP-400 Aero Sport Power, replaced with Lyc Thunderbolt 390
RV-6A sold
Sport Pilot (weight-shift control) - Airborne XT912
Dues paid 9/2020
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